English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

We present new photometric and spectroscopic observations for 2M 1533+3759 (=NSVS 07826147). It has an orbital period of 0.16177042 day, significantlylonger than the 2.3--3.0 hour periods of the other known eclipsing sdB+dMsystems. Spectroscopic analysis of the hot primary yields Teff = 29230 +/- 125K, log g = 5.58 +/- 0.03 and log N(He)/N(H) = -2.37 +/- 0.05. The sdB velocityamplitude is K1 = 71.1 +/- 1.0 km/s. The only detectable light contributionfrom the secondary is due to the surprisingly strong reflection effect. Lightcurve modeling produced several solutions corresponding to different values ofthe system mass ratio, q(M2/M1), but only one is consistent with a core heliumburning star, q=0.301. The orbital inclination is 86.6 degree. The sdB primarymass is M1 = 0.376 +/- 0.055 Msun and its radius is R1 = 0.166 +/- 0.007 Rsun.2M1533+3759 joins PG0911+456 (and possibly also HS2333+3927) in having anunusually low mass for an sdB star. SdB stars with masses significantly lowerthan the canonical value of 0.48 Msun, down to as low as 0.30 Msun, weretheoretically predicted by Han et al. (2002, 2003), but observational evidencehas only recently begun to confirm the existence of such stars. The existenceof core helium burning stars with masses lower than 0.40--0.43 Msun impliesthat at least some sdB progenitors have initial main sequence masses of1.8--2.0 Msun or more, i.e. they are at least main sequence A stars. Thesecondary is a main sequence M5 star.

Modeling the System Parameters of 2M1533+3759: A New Longer-Period Low-Mass Eclipsing sdB+dM Binary